Updated 05/20/12 – 3:58 p.m.

CHICAGO (CBS) — Cook County prosecutors said Sunday that one man arrested earlier this week in connection with the NATO Summit said he could blow up a downtown bridge, though it turned out he didn’t have a bomb. Another man allegedly asked others to get him materials to make a pipe bomb.

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Bond was set at $750,00 on Sunday for 24-year-old Sebastian Senakiewicz, who was charged with making a false terrorist threat. He had been arrested at his home in the 3600 block of North Odell Avenue on Thursday.

Prosecutors said Senakiewicz is a Polish native and self-proclaimed anarchist who was upset with the lack of chaos in Chicago leading up to the NATO Summit. He allegedly bragged he could blow up a downtown bridge and that he was keeping explosives in a hollowed-out Harry Potter book.

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He also allegedly claimed he had a vehicle packed with explosives and weapons, and that he had enough homemade explosives to blow up a train overpass during the summit.

Acting on a search warrant at his house, Senakiewicz was arrested on Thursday, but no explosives were found.

A second man arrested Thursday, 28-year-old Mark Neiweem, was ordered held on $500,000 bond. Prosecutors said he wanted to build a pipe bomb and wrote up a list of ingredients, asking others to get him the materials. He was charged with attempted possession of explosives.

According to prosecutors, Neiweem met with associates at a Cook county forest preserve on Tuesday, and asked one of them if they had “funds for fun.” The two walked away from the rest of the group, and once alone, Neiweem allegedly told his associate that he wanted to get materials to make a pipe bomb. He said he needed a PVC pipe, two PVC caps, PVC glue and several model rocket engines.

When they later left the forest preserve, Neiweem allegedly wrote out a list of the ingredients he wanted, gave it to his associate, and said if the other person brought the items to his house, he would build a pipe bomb.

Prosecutors said, although both cases stemmed from related investigations, they are separate matters.

The two men were the fourth and fifth anti-NATO activists to be arrested this week, in advance of the NATO summit.

Their cases did not appear to be related to the arrests of three other men on terrorism charges last week, for allegedly plotting to use Molotov cocktails to attack police stations, the mayor’s home and President Barack Obama’s campaign headquarters.

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The two men’s defense attorneys denied any wrongdoing and said both instances were cases of entrapment by undercover police officers, or police informants.

Defense attorney Sarah Gelsomino said the charges against the two men not related to the charges against the three men arrested in a raid in Bridgeport last week. But she said there is a similar pattern.

“We do believe that the same police informants that ingratiated themselves with the three who were charged yesterday, and manufactured any type of alleged criminal activity, were also involved in these two cases,” she said. “The allegations raised against these two in court today stem from – once again – the minds of the two informants, who we believe to have been working since May 1, for the Police Department.”

Those three, who have been charged with possessing explosives to commit terrorist acts, were witnessed by undercover police investigators making the fire bombs inside an apartment in Bridgeport, authorities say. They have been under surveillance for several days and arrested on Wednesday.

Lawyers for Brian Church, 20, of Ft. Lauderdale, Fla.; Jared Chase, 24, of Keene, New Hampshire; and Brent Vincent Betterly, 24, of Oakland Park, Fla., insist the only thing inside that apartment was beer-making equipment.

But Cook County State’s Attorney Anita Alvarez said surveillance has proven that their plans were far more sinister, and could have hurt or killed people in Chicago.

Specifically, Alvarez said the group planned to attack police cars and four Chicago Police stations with “destructive devices.” The attacks on police were intended to be a diversionary tactic to undermine the police response to other attacks, Alvarez said.

“Some of the proposed targets included the campaign headquarters of President Barack Obama, the home of Mayor Rahm Emanuel, and certain downtown financial institutions,” Alvarez said.

The group also allegedly was conducting surveillance on Chicago Police Headquarters.

Sources said the trio was part of the Black Bloc method of violent anarchist protesting/rioting that began in Europe in the 1970s. In the Black Bloc method, protesters often dress all in black and cover their faces, as they destroy property and try to pick fights with police officers.

Sources told CBS 2 that this Black Bloc group had late night training sessions and part of their efforts could have included improvised explosives, swords, hunting bows, throwing stars and brass knuckles.

At one point, one member of the group allegedly said: “The city doesn’t know what it’s in for. After NATO the city will never be the same.”

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All three are being held on $1.5 million bonds.